Electrical control circuits



May 11, 1965 F. H. HOLLAND 3,183,377

ELECTRICAL CONTROL CIRCUITS Filed May 3, 1961 4 Sheets-Shevt 1 l'FRANKH. HOLLAND May 1l, 1965 F. H. HOLLAND 3,183,377

ELECTRICAL CONTROL CIRCUITS Filed May 3, 1961 4 Sheets-Sheet 2 AIRSOURCE as a? 2e 29 I d J5- Fs F /g. 2 ,4 o Lm `R2 R5 CQNTACTS CONTACT 5oc. OPERATION 54556 97074 CONTACT 3| l:- RU" X x CONTACT s2 l:- coNTmuousx x x x ,NCH x x CONTACT 35 Il l- DENOTES CLOSED Fig. 4

X DENOTES CLOSED Fig. 3

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May 11, 1965 F. H. HOLLAND 3,183,377

ELECTRICAL CONTROL CIRCUITS Filed Nay s, 1961 4 Sheets-Sheet 3 CONTACTso ACONTACT n3 El: CONTACT 3| a CONTACT "4l- CoNTACT 32 lcoNTAcT N5:-CoNTACT sa I CONTACT N2 E l DENOTES CLOSED Y [L /g 7 INVENTOR FRANK H.HOLLAND May 11, 1965 F. H. HOLLAND 3,13,377

ELECTRICAL CONTROL `CIRCUITS Filed May s, 196i 4 sheets-sneer 4INVENTOR.

FRANK H. HOLLAND United States Patent O 3,183,377 ELECTRICAL CONTROLCIRCUITS Frank H. Holland, Cleveland, Ohio, assigner to The ClarkController Company, Cleveland, Ohio, a corporation of Ohio Filed May 3,1961, Ser. No. 123,603 34 Claims. (Cl. 367-113) My invention relates toelectrical control circuits and more particularly to electrical controlcircuits for safely controlling the operation of a punch press.

Punch presses may be of many varied sizes and types. One type utilizes acontinuously running motor driving a flywheel. The iiywheel is engagedwith and disengaged from the press shaft by means of an air operatedclutch. An air operated brake is utilized to rapidly stop and hold thepress when desired. An air valve is utilized to control the flow of airfrom an air source to the clutch and brake, and the air valve iscontrolled by a winding on an electromagnet.

A second type of punch press utilizes an eddy current clutch and brakewhich perform the same functions as the air operated clutch and brake.The eddy current brake and clutch are controlled by an electromagneticwinding. The eddy current brake is used in stopping the press and afriction brake is used to assist in stopping and to hold the press.

Another type of punch press is a direct connected press. Here the motoris connected directly to the press ram and the operation of the pressram is controlled by the starting and stopping of the motor. The motoris controlled by a starter having an electromagnetic winding. A frictionbrake is also used to stop and hold the press when desired.

In the normal operation of most presses, the operating personnel arerequired to place their arms between the dies of the press to feedmaterial to the press, remove the punched parts from the press, and toclean the press. It is therefore seen that presses are potentiallydangerous should the control equipment malfunction causing the press tooperate when not desired.

Therefore, it is the primary requirement that control for operating apunch press provide the optimum in ultimate safety to personnel,protection for the expensive equipment while still maintaining Ithemaximum production rates.

Heretofore, press control systems have been devised whereby the operatoris required to keep his hands on separate push buttons during the timethat the press ram is moving downward to engage the dies. One suchcontrol system is illustrated by United States Letters Patent Number2,299,007.

However, these systems were not capable of protecting against changesmade by the operators themselves in order to increase their piece rate,nor were they capable of protecting against the mulfunction of thecontrol components.

It is therefore the primary object of my invention to provide a presscontrol circuit which will overcome the above mentioned difficulties.and which will provide maximum safety in its operation.

It is another object of my invention to provide a press control circuitwhich prevents operation should any of the normally open contacts of theoperators push buttons be short circuited.

It is still another object of my invention to provide a press controlcircuit which will stop the operation of the press should the limitswitches or their contacts not be operating properly.

A further object of my invention is to stop the press should a controldevice connected in the circuit fail to operate properly when requiredto do so.

A still further object of my invention is to provide a press controlcircuit which requires that all operators push buttons be releasedbefore the press can be restarted at any point in its operating cycle.

The present embodiment of my invention utilizes a pair of push buttonsfor each operator, each push button has a normally open and a normallyclosed contact. A first contactor is connected to be energized throughthe normally colsed contacts of the push buttons. Once energized, theirst contactor holds itself in through its own contacts.

A second contactor is connected to be energized through the normallyopen contacts of the push button and normally open contacts of the firstcontactor. When the push buttons are depressed by the operator, thesecond contactor is energized through the described circuit to operateand close its contacts. The second contactor then is maintainedenergized through the normally open contacts of the push buttons and itsown contacts. A contact of the second contactor is connected so whenoperated, it opens the energizing circuit of the first contactor,causing it to become ie-energized.

A third contactor is connected to be energized through normally opencontacts of the second contactor and normally closed contacts of thefirst contactor and the normally open contacts of the push buttons.

After operation of the third contactor, the device controlling theoperation of the punch press, the air valve or main motor starter, asthe case may be, is energized through the normally open contacts of thepush button, the normally closed contacts of the rst contactor andnormally open contacts of the second and third contactors.

The press is then connected to operate and its ram moves downward.Should the operator remove either hand or both from the push buttons,the normally open contacts of the push button will open the circuitenergizing the press controlling device and the press will stopimmediately. The second and third contactors are also de-energized, andthe operator must release both push buttons to re-energize the firstcontactor. Then, depress both push buttons to re-energize the second andthird contactors before he. can restart the operation of the press.

Contacts of cyclically timed switches are connected in the circuit sothat after the press ram has gone beyond the point where the operatorcannot injure himself, the energization of the press operating device istransferred from the normally open contacts of the push buttons to thecontacts of the cyclically timed switches. These contacts open at theend of each stroke to stop the press, unless the operator has properlyreleased and then depressed the push buttons.

Throughout the operation cycle of the press, the components of thecircuit are checked by the operation of the circuit to ensure that theyhave operated properly. If one of the components should fail for anyreason whatsoever, the press will stop when it reaches the point in theoperating cycle where the failed device is checked or should haveoperated.

A second embodiment of my invention protects against false operation ofthe press should the normally open contacts of the push button becomeshort circuited. For presses having only one operator, a single pair ofpush buttons is used and the first contactor is replaced by twocontactors. Each contactor is connected in series with a different oneof the normally closed push button contacts. Therefore, if one of thepush button normally open contacts is shorted, the second contactorcannot become energized to operate the press if only one push button isdepressed.

For presses having more than one operator, a setup contactor isconnected to be energized through the normally closed contacts of allthe operator push buttons. When this contactor is energized, its variouscontacts set up a circuit for each norm-ally open push button contact toconnect one side of the source to a latch relay. If any of the normallyopen contacts are shorted, the latch relay operates and mechanicallyholds its contacts operated to prevent operationrof the press. The otherside of the latch relay is connected to the other side of the sourcethrough the push button normally closed contacts. Because it isdesirable to have one each of the push button pairs on either side ofthe line, it is necessary to have two latch relays, one to check thenormally open contacts on each side of the source.

A third embodiment of my invention checks the limit switch contacts fromfailure to operate or from the limit switch from becoming disconnectedfrom the press. This is accomplished by having a second limit switchseparately connected to the press and connected into the circuit so thatit is mandatory that the limit switch contacts operate properly eachcycle of press operation. If they do not, the power is removed from thecircuit causing the press to stop.

Many other objects and advantages of my invention wiil become readilyapparent to those skilled in the art when'the following description isread with reference to the drawings in which:

FIGURE 1 is a schematic representation of the circuit for operating thepress controlling device;

FIGURE 2 is a diagrammatic representation of a press and its operatingequipment;

FIGURE 3 is a diagrammatic representation of a selector switch toillustrate the condition of its contacts in its various operatedpositions;

FIGURE 4 is adiagrammatic representation of the condition and operatingpoints for the contacts of the limit switches in FIGURES 2 and 5 withrespect to the press operating cycle;

, FIGURE 5 is a schematic representation of a press control circuit toillustrate `another embodiment of my invention;

FIGURE 6 is a schematic representation of a press control circuitillustrating a variation from FIGURE 5;

FIGURE 7 is a diagrammatic representation of the Y condition andtheoperating points for the contacts of the two limit switches of FIGURE 6with respect to the operating cycle of the press.

Reference is first made to FIGURE 2 which illustrates part of an airclutch typer press mechanism, it being understood that my'invention canbe used with other types of presses and that reference to thisparticular type Y of press mechanism is made only, toY describe a modeof operation, as is required by law.

A main shaft It? of the press is provided with cranks II--Il toreciprocate the press ram,in a well known manner, and is rotatablysupported in bearings on a main frame 12. Shaft ttt is driven by a motor13 through a motor pinion 14 land a gear 15. Gear 15 has a hub I6 and'isnormally rotated idly on main shaft It like a flywheel.

Motor I3 is connected to a source of A.C. supply I7 by lines 18, 19 and2t?.

A pneumatic cylinder 21, supported on main frame 12 I; of the press, hasa piston 22 therein with a piston rod 23 projecting therefrom. by aspring 24.

Hub 16 and piston rod 23 project into a clutch and Piston 22 is normallyretracted brake mechanism indicated diagrammatically at 25. 'flicVmechanism comprises elements,.by'which, when piston Z2 Vis retracted byspring 24, the brake grips shaft ttl and When piston'rod 23isfprojectedV forbehind piston 2 2, the brake, is

stops the press.

4 released and hub 16 Vis connected to shaft 10 by the clutch to causegear I5 to'drive shaft 10 and the press. The clutch is released whenpiston rod 23 is retracted to its rearward position by spring 24.

On the free end of shaft It are mouted cams 26 to 29 that rotate withshaft It) and operate contacts 30 to 33, respectively, to open `andclose them. The cams are adjustable around shaft I0 to cause thecontacts to operate at preselected times or points in the press cycle.In most practical applications, the cams and cam operated contacts arenot an integral part of the press, but takeV the form-of a limit switchwhich is mechanically connected to shaft Itl.

An air valve housing 34 communicates with a source of air 35 underpressure. Within housing 34tis a main valve, not shown, controlled by areciprocal pilot valve indicated at 36. Pilot valve 36 is reciprocatedto its operated position upon energization of a winding 37 of anelectromagnet 3S. When winding 37 is energized, the main valve isoperated by air pressure to effect communication of air pressure througha conduit 39 tovcylinder 21 and moves piston 22 and rod 23 forwardly tooperate clutch and brake mechanism 25, starting operation of the press.

When winding37 is cle-energized, a spring 4t) restores pilot valve 36,causing the main valve to restore and cut off communication of tiuidpressure to conduit 39 and open exhaust conduit d1. Cylinder spring 24returns piston rod 23 and operates clutch and brake mechanism Z5 torelease the clutch `and set the brake to stop the press. Y

YPart of the energizing circuit at 4t2-43.

The air valve described above, operating responsive to energization andde-energization of a winding, and shown diagrammatically in FIGURE 2,may be that constituting the subject matter of United States LettersPatent 2,902,- 052, issued on September 1, 1959 to which reference maybe had for structural details.

In FIGURE 1, which illustrates the invention as applied to presscontrols, the aforesaid contacts 30 to 33, the

for winding 37 is shown velectromagnet 38 and its winding 37 and theenergizing circuit 42-43 are reproduced from FIGURE 2 with the samereference numerals. Y

Wires 44 and 45 are connected toa suitable source of alternatingcurrent. Wire 45 directly, and wire 44 through a normally closed stoppush button 45 and a wire 47.

Connected across wires 44 and 45 is a contactor F having a winding 43and normally open contacts FI through F5 and a normally Vclosed contactF6. The circuit consists of a start push button 49, contact ZCRS,contact SCRS, contact 50 of a key operated selector switch, contact R5,winding 48.

Contact F4 is connected in parallel with start push button 49, contactZCRS and contact CR5.Y Contact R4 is connected in parallel with contactF4. i

Asecond contactor R, having a winding 51 and normally open contacts R1through vRd and normally closed contact R5, is connected in parallelwith key operatedV selector switch contact 50, contact R5 Vand winding48 ofY contactor F. This circuit consists of a second contact 52' Vofthe key operated selector switch, contact F6 and winding 51 of contactorR. Y Contacts F1 to F3 of contactor F, when closed, connect motor 13 tosource 17 through wires 18, 19 and 2t! to Voperate motor 15in theforward direction (see FIG- UREy 2).

Contacts R1 to R3 of contactor R, when closed, con- Y neet motor I3 tosource 17 through wires 18, 19 and 20 toY operate motor I3 in thereverse direction.

A contactor ICR, having a winding 53 and normallyj open contacts ICRI toICR4 and normally closed contacts 1CR5 and ICRS, isconnectedracrossilines 44 and contacter ICR, contact 1CR2, contact 2CR7and selector switch contact 55. Normally closed contact 56 of a pushbutton 57 is connected in parallel with contact 2CR6 and contact lCRl.Similarly, normally closed contact 58 of a push button 59 is connectedin parallel with contacts 1CR2 and 2CR7.

A wire Gil is connected to this circuit between Contact F and contact2CR6. A second wire 61 is connected to this circuit between contact 2CR7and -selector switch contact 55.

A contactor ZCR, having a winding 62 and normally open contacts 2CR1 to2CR4 and normally closed contacts 2CR5 to 2CR9, is connected acrosslines 60 and 61 by a circuit consisting of normally open contact 63 ofpush button 57, contact 1CR3, winding 62 of contactor 2CR, contact 1CR4,and normally open contact 64 of push button 59. Contact 3CR6 and contact2CR1 are connected in parallel with contact 1CR3. Contact ZCRZ isconnected in parallel with contact 1CR4. Contact 3Q of the cyclicallytimed switch is connected in parallel with contact SCRS.

Another contactor SCR, having a Winding 65 and normally open contacts3CR1 to 3CR4 and normally closed contacts 3CR5 to 3CR7, is connectedacross wires 60 and 61 by a circuit consisting of contact 63 of pushbutton 57, Contact lCRS, contact 2CR3, Winding 65 of contactor SCR,contact ZCRS, contact ZCR4, contact 1CR6 and contact 64 of push button59. Contact 33 of the cyclically timed switch is connected in parallelwith contact ZCRS.

A second circuit connects winding 65 of contactor 3CR to wires 60 and 61and consists of contact 31 of the cyclically timed switch, contact 3CR1,winding 65, contact ZCRS, contact 3CR2 and contact 32 of the cyclicallytimed switch.

Connected between contact 31 and contact 3CR1 is a circuit consisting ofwire 66, contact SCRS, wire 42, winding 37 of the air valve, wire 43,contact 3CR4 and wire 67 which connects between Contact SCRZ and contact32.

Selector switch contact 68 is connected in parallel with switch 31.

Selector switch contact 69 is connected in parallel with switch 32..

Winding 37 of the air valve may be connected directly to lines 44 and 45by an inching circuit. This consists of selector switch contact 70,normally open contact 71 of an inching push button 72, contact 2CR9,wire 42, winding 37, wire 43, contact 3CR7, contact 73 of inching pushbutton 72 and selector switch contact 74.

FIGURE 3 represents the position ofthe selector switch contacts 54, 55,68, 69, 70 and 74 for the various types of press operation. Selectorswitches of this type are readily available. When desired to run thepress, the selector switch is rotated to close contacts 54 and 55leaving the remaining contacts open. When desired to operate the presscontinuously, the selector switch is rotated to close contacts 54, 55,68 and 69 leaving the remaining contacts open. When desired to inch thepress, the selector switch is rotated to close contacts 79 and '74 andopen contacts 54, 55, 68 and 69.

Operation To begin operation, the operator must turn the key operatedselector switch so contact 50 is closed and contact 52 is open. Startpush button 49 is then depressed to energize winding 48 of contactor Fthrough the aforedescribed circuit. Contactor F operates to closecontacts F1 to F5 and open contact F6` Contacts F1 to F3 operate toconnect motor 13 to source 17 through lines 18, 19 and 2i? in a mannerto be operated in the forward direction.

Contact F4 closes and connects winding 48 of contactor F to line 44 sothat the operator can now release start button 49.

Normally, a press is operated in one of three methods.

One is to inch the press. This is to connect the press so that it willoperate only as long as a push button is held depressed. By this means,the movement of the press ram can be controlled for extremely shortdistances and is used primarily to ensure the mating of dies whensetting up a press.

Another type of operation is to run the press. This method of operationis used most of the time in the press productive operation. Here, thecontrol is connected so that each operator must depress a push buttonwith each hand to start the press operation. The press continues in itsoperation only if the push buttons are held depressed and will stopautomatically at the end of each cycle of operation. The push buttonsmay be released as soon as the press ram has passed the point at whichit Would be dangerous to the operators hands. During this interval, theoperators may release the push buttons and use their hands to remove thefinished work from the press throat and put a new piece of raw materialin the dies.

The third method is the continuous method of operating =a press. Inthese instances, the material is automatically fed into and retractedfrom the press sothat it can run continuously once its initial operationis started.

Once the type or" operation has been determined, the selector switch ismoved to the proper position. Normally, this selector switch is of thelock type so that it cannot be operated by unauthorized individuals.FIG- URE 3 is a diagrammatic representation of the selector switch andindicates which contacts are closed for the Various types of operation.

When the selector switch is moved to its run position, contacts 54 and55 become closed. Thus, with contact F5 closed, contactor 1CR isenergized through normally closed contacts 56 and 58 of push buttons 57and 59, respectively. Winding 53 of contactor ICR is energized andcontactor CR -operates to close contacts 1CR1 and 1CR4 and open contacts1CR5 and 1CR6.

After contacter 1CR becomes energized, the circuit is in the state readyfor operation.

Depending upon the type and the size of the press, it may have one ormore operators. While the circuit of FIGURE 1 Ishows only two pushbuttons, 57 and 59, it is noted that when more .than one operator isrequired, an additional pair of push buttons must be added for eachoperator. When this is done, one of the pair is connected in series withpush button 57 and the other of the pairs is connected -in series withpush button 59. This requires that the operators must depress all of thepush buttons and maintain them depressed while the press is goingthrough its unsafe portion of its operating cycle.

To operate, the operator must depress push buttons 57 and 59 to opencontacts 56 and 58 and close contacts 63 and 64. The closing of contacts63 and 64 connects winding 62 of contactor ZCR so it is energizedthrough contact 63 of push button 57, contact 1CR3, contact CRft, andcontact 64 of ypush button 59. Contactor 2CR operates to close contacts2CR1 and 2CR4 and open contacts ZCRS to 2CR9.

Even though the depression `of push buttons 59 and 57 opened contacts 56and S8, contactor ICR remains energized through contacts lCRl and 1CR2.As soon as contactor ZCR becomes operated, contacts 2CR6 and 2CR7 open,-to de-energize contactor 1CR and contacts lCRl to 1CR6 return to theirunoperated position.

Contactor ZCR is now maintained energized through contacts 3CR6 and 2CR1in parallel with contact 1CR3, and contact ZCRZ which is in parallelwith contact 1CR4. It is also maintained energized by limit switchcontact 3i? which is in parallel with contact 3CR6.

It is seen that should the operator release either or both of the pushbuttons 57 and 59, the opening of either contact 63 or 64 wouldde-energize contactor ZCR. If only one push button was released, hewould have to release the other one to re-energize contactor ICR and,laser then depress both push buttons again to re-energize contactorZCR.

The reclosing ot contacts ECRS and iCRo now connect winding 65 ofcontactor SCR so it is energized through contact 63 of push button 57,contact lCRS, contact ZCRS, winding 65 of contactor SCR, limit switchcontact 33, contact ZCRi, contact lCRo and contact oli of push button S.Contactor SCR operates to close contacts SCRi to SCRL.A and opencontacts 3CR5 to 3CR'7.

The closing of these contacts connects winding 37 so it is energizedthrough contact o3 of push button 57, contact lCRS, contact 2CR3,contact CRl, wire do, contact SCRS, wire 42, winding 37, wire d3,contact -SCRL wire 67, contact ECRZ, cont-act ZCRLi, contact liCR, andcontact 64 of push Ibutton 59.

Winding 37 is now energized so electromagnet 38 operates to operate theair valve and air under pressure is supplied by conduit 39 to cylinder2.1 behind piston 22. Piston 22 is moved forwardagainst the bias ofspring Zd and causes piston rod 23 to disengage the brake and engage theclutch. Gear i5 is connected to shaft tti to cause the press to beginits cycle of operation.

When contactor SCR operates to open contact 3CR6, contactor ZCR ismaintained energized by parallel connected limit switch contact 39.

FIGURE 4 is a diagrammatic representation of the portion of the presscycle of operation that each of the individual limit switch contacts areopened and closed. It is noted at the beginning of the cycle that limitswitch contact 3i) is maintained closed until approximately 180 of thepress cycle. This is the point at which the press ram has reached itsmaximum down stroke. lit is also noted that limit switch contacts 3l and32 become closed shortly before limit switch contact 59 opens. Further,limit switch 33 remains closed throughout the major portion of the presscycle and opens only momentarily `at about the press 270 portion.

Therefore, when limit switch contacts 3i and 32 close, contactor SCR andwinding 37 are energized directly from wires 6i? and 6i and, thus, pushbuttons 57 and@ need no longer be held depressed by the operator. It isto be -noted Vhere that since the press ram has reached the bottom ofits stroke, the operator cannot injure vhimself by putting his hand inthe press throat.

Contactor SCR is maintained energized by the circuitY consisting oilimit switch contact 3i, contact 3CR1, winding o5 of contactor SCR,limit switch contact 33, contact CRZ and limit switch contact 32.Likewise, winding 37 is energized through the circuit consisting oflimit switch contact 3l, wire 66, contact SCRS, wire 42a',` winding 37,wire 43, contact SCRK, wire 67 and limit switch contact 32.

As soon as limit switch contact 3i) opens, winding 62 of contactor ZCRbecomes de-energized and its contacts ZCRl to ZCR@ return to theirnormal condition,

The press continues to operate as described until it reaches the 360point of its cycleof operation at which point limit switch contacts 31and .'52 open to dc-energize contactor SCR and winding 37.

The de-energization of winding 37 allows electromagnet 38 to reieasepilot valve 36 and it moves up under the bias oi its spring liti. Theair valve becomes unopK erated and shuts od the supply of air fromcylinder 21 and allo-ws the air in conduit 3S and cylinder 2i to eX-haust back and out through conduit 4,1.

Piston 22 and piston rod 23 are moved rearward by the bias of spring A24to disengage the clutch and set the brake to .stop further movement ofthe press.

It is to be noted that limit switch contact 33 Vopened at approximately270 of the press cycle, but that winding @d ofcontactor SCR wasmaintained Yenergized through contact ZCRS, which is connected inparallel with limit switch contact This operation of limit switchcontact 33 checked the operation of contactor ZCR to make sure that itbecame deenergizedproperlyl it had not, the opening of limit switchcontact 33 would cause contactor BCR to become `cte-energizedimmediately to stop the press.

Had the operator maintained push buttons 57 and 59 depressed, contactorZCR would still become deenergized and unoperated when limit switchcontact Sti opened. Also, when limit switch contacts 31 and 32 opened atthe end of the machine cycle, contactor SCR and winding '37 would stillbecome de-energized because ot contacts ZCR3 and ZCRI connected in itsenergizing circuit.

After the operator has released push buttons 57 and I S9 and limitswitch contact Si? has opened to de-energize contactor ECR, contactorICR Ywill'becorne energized, as described, and ready for the next cycleof operation.

'it is seen that should the operator release his hands from either orboth push buttons 57 and 59 during the iirst of the press cycle, eithercontact 63 or contact 6dor both ot them open the energizing circuit towinding to stop the press. This also opens the energizing circuit forcontactors'ZCR and SCR and they become 'de-energized. However, since theenergizing circuit for winding e2 of ZCR is through contacts llCRS andlCRd, it is necessary that the operator release both push buttons 57 and5%, at the same time, to re-energize contactor iCR, and then re-depressboth push buttons to re-energize contactor ZCR.

ln applicationsY ot this type, it isV desirous to not stop the press atthe end o each cycle provided the operators have had an opportunity toremove the finished material from the dies and insert the new materialtherein before the end of the cycle. This is referred to as jumping thepress and is accornpiished as follows.

As soon as the operators have accomplishedthis work, and provided it isafter the `press has reached the point in its cycle where limit switchcontact 3i) has opened and again reclosed7 all the operators may puttheir hands back on the push buttons and depress them. This will bringin contactor ZCR in the same manner as before described and causecontactor iCR tobecome de-energized. Contactor ZCR is maintainedenergized through its own contacts and limit switch contact 39, whichagain closed shortly after the point in the press cycle' that limitswitch contact 33 reclosed.V Therefore, contactor SCR and winding 37 aremaintained energized by current through the contact 63 of push button 57and contact 6d of push button S9 in the circuit as before described andwill not become cie-energized at the end of the cycle, when limit switchcontacts 31 and 32 opened. Jumping the press is provided to facilitateproduction, yet allows it to be done only if all of the operators workhas been accomplished Yand their hands in the safe position on the pushbuttons.

Should it be desirous to operate the press in its continuous condition,the selector swit'clr'is turned to its continuous position whereselector switch'contacts 68 and 69 are closed aiong with contactsfd and55. in this type` of operation, the initial starting of the press isaccomplished in the same manner as aforedescribed. However, iminediateiyafter starting movement of the press, the operator can remove his lhandsfrom both push buttons and the press will continue to operate'until astop button, such as do, is depressed. lf desired, a stop button may .beconnected in series with selector switch Contact so only the presscontrol circuit may be' deenergizcd and not that of mot-or i3.

Continuous operation is accomplished as follows, With Vpush Ybuttons 57and 59 in theirk up position, contactor llCR is energized to operate itscontacts. The operator may then push the push buttons to close contacts63 and 64, and open contacts 56 and58. Contact orY CR is'energizedthrough contacts llCR3 and lCRi and' rnaintainedV energizedithroughitslown contacts, ZCRl and ZCRZ, and limit switch contact 3o. ContacterYLCR Yis 9 de-energized by contacts 2CR6 and 2CR7 and becomesunoperated.

Contactor SCR is operated by current through push button contact 63,contact ICRS, contact 2CR3, winding 64 yof contactor SCR, limit switchcontact 33, Contact 2CR4, contact ICR6 and contact 64 of push button 58.

As soon as contactor SCR becomes operated to close its contact, winding37 becomes energized as before described. Since selector switch contacts66 and 69 are closed for continuous operation, contactor SCR is nowmaintained energized from wire 60 directly through selector switchcontact 68, contact BCRI, winding 65 of contactor SCR, limit switchcontact 33, contact 3CR2, and selector switch contact 69 to wire 6I.Winding 37 is also maintained energized directly by the circuitconsisting of selector switch contact 68, wire 66, contact 3CR3, wire42, winding 37, wire 43, contact 3CR4, wire 67 and selector switchContact 69 to wire 6I.

The operator may now release his hands from the push buttons, completelyindependent of the position of the press ram. Contactor ZCR then becomesde-energized to close contact ZCRS and maintains contactor SCR and itswinding 65 energized through closed Contact ZCRS, which is parallel withlimit switch contact 33. The press will now continue to operatecontinuously until such time that the operator pushes a stop button toremove the power from the press control circuit.

For the other type or inching operation, the selector switch is turnedto the inching position, at which point, selector switch contacts 70 and74 are closed and selector switch contacts 54, 55, 68 and 69 are opened.By pushing inching push button 72, the operator can connect winding 37directly to the source by lines te and 45 through the circuit consistingof selector switch contact 7G, contact 7I of push button 72, normallyclosed Contact 2CR9, wire 42, winding '37, wire 43, contact 2CR7,contact 73 of push button 72 and selector switch contact 74. In thistype of operation, the press will operate when push button 72 isdepressed and will continue to operate only as long as it is helddepressed. This is true completely independent of the position of theram in the press operating cycle. As before described, the use of thistype of operation is primarily in the settingy up and the matching ofthe press die.

FIGURE 5 is similar to FIGURE I except it has the added feature ofprotecting against the possible short circuiting of the push buttonsnormally open contacts when only two push buttons are used. Therefore,like parts have been given the same reference characters, and only theportion of FIGURE l necessary to described the feature has been shown.

Contactor ICRA has a winding 75 and normally open contacts `ICRAI andICRAZ and normally closed contacts ICRA3 and ICR/3x4. It is connectedacross wires 6i) and l6I by normally closed contact 56 of push button57. Contacts ICRAI and 2CR6 are connected in parallel wit-h contact 56.

Contacter ICRB has a winding 76 yand normally open contacts ICRBI andICRBZ, and normally closed contacts ICRBS and .ICRBe It is connectedacross wires 6d) and 61 by normally closed contact 58 of push button 59.Contactors ICRBI and 2CR7 are connected in parallel with contact 53.

The remainder of the circuit for FIGURE 5 is identical with that ofFIGURE l except that contact ICRAZ replaces contact ICRll, contact ICRBZreplaces Contact IiCRZ, contacts ICRAS and ICRB3I replace contact ICRS,and .contacts ICRA4 and ICRB4 replace contact ICR6.

Therefore, the operation of the two circuits to energize winding 37 areidentical except that whenever contactor ICR operated in FIGURE 1 Ibothcontactors ICRA and ICRB yoperate in FIGURE 5. Itis believed that theoperation of FIGURE 5 for the normal modes of operation described forFIGURE l are understood, and for the sake 10 of brevity, a completere-description of these modes of operation will not be made.

As stated, FIGURE 5 protects against the possible short circuiting ofeither normally open push button contacts 63 or 64. This is as follows.

Assuming that contact 63 has become shorted due to an accident,contactor ZCR still cannot become energized because of contact 64 beingopen. However if only push button 64 is depressed, an unsafe conditionis created since the operators other hand is free and therefore, thepress should not be allowed to operate. When this occurs, contactor ZCRoperates its contacts. The opening of contact 2CR7 causes contactor ICRBto become deenergized. Contactor `ICRA does not become de-energizedsince it is maintained energized through contact 56 of push button 57which has not -been depressed.

Therefore, contacts -ICRA3 and ICRA4 in the energizing circuit forcontactor SCR remain open to prevent it from becoming energized. Thus,winding 37 cannot become energized and the press will not operate.

If both push buttons 57 and 59 are depressed when contact 63 is shorted,the press will operate in the normal manner. However, since :both pushbuttons are depressed, an unsafe condition does not exist and operationof the press will not be harmful or dangerous.

It is to be noted that the circuit of FIGURE 5 can only be used with twopush Ibuttons or one operator. If more than one operator is required,which necessitates the use of -rnore than two push buttons, the circuitof FIGURE 6 must be used.

Here again, FIGURE 6 is very similar to FIGURES I and 5, and like partsof the two figures have been given the same reference characters. Also,only that portion of FIGURE I necessary to describe the feature has beenshown.

FIGURE 6 has four push buttons 77, 73, 79 and 86. Each push button has anormally open Contact SI, 82, 83 and S4, and a normally closed Contact85, 86, 87 and 88, respectively.

The normally closed contacts are connected from wire 60 by a wire S9,contact 8S, contact 86, a wire 9i), winding 91 of a contactor CR, a wire92, contact 87, contact 88 and a wire 93 to wire 6-1.

Contacter 96 has normally open contacts CRI to CR6 and normally closedcontacts CR7 to CRIQ.

A first latch relay ISR having a latching winding 94 is connected bythree possible separate circuits between wires 92 and 60. Latch relayalso has a trip winding 95 and a normally open Contact ISRI and normallyclosed contacts ISRZ and ISR3.

The first of the possible circuits is through a normally open contact 96of a first selector switch 97 and a normally open contact 98 of a secondselector switch 99 to wire 60. 'Ihe purpose of selector switches 97 and99 will be described in more detail hereinafter.

The second circuit is through contact CRI, a normally closed contact 16)of selector switch 99, contact 84 of push button Si) to wire 66.

The third circuit is through contact CRI, a normally closed contact Itllof selector switch 97, contact 83 of push button 79, and contact (SR2 towire 66.

A second latch relay ZCR having a latching winding I6?. is connectableby two possible separate circuits between wire and wire 6I. Latch relayZSR also has a trip .winding 163 `and a normally open contact ZSRI andnormally closed contacts ZSRZ and ZSRS.

The `lrst possible circuit is through Contact CRS, a normally closedcontact IM of selector switch 97, contact 82 of push button 78 andcontact CIMl to wire 6l..

The second circuit is through contact CRB, a normally closed contact IGSof selector swltch 99, and contact SI of push button 77 to wire 6I.

Trip windings and 163 are connected in parallel with each other and inseries with a normally open contact 14.76 across wires 66 and 6I.

Contacts lSRl and ZSRl are connected in parallel with each other and inseries with an indicating 'lamp 107 across Wires et? and 6l.

The normally open contact ofthe push butt-ons are connected from Wire60, contact 34, contact CR?, contact 83, contact CRS, contact lSRZ,contact ZSRZ, contact ECR-3, Winding 52 of contactor ECR, contactTCR-1t, contact 2SR3, contact llSRS, contact CRS, contact 32?., contactCRM, and contact 3l to wire 6l.

Contactor TCR is connected across wires o@ and el by contact CRS,Winding 53 of contactor E CR and con tact CR6. Contacts 2CR6 and lCRlare connected in series with each other and in parallel with contactCRE. Contacts lCRZ and ZCR? are connected in series wit-l1 each otherand in parallel with contact CR6.

A second indicating lamp Hi8 is connected across Wires 6i) and 6l by acircuit from wire 60 consisting of wire 89, indicating lamp 108,normally open contact 109 of selector switch 9'! to wire 6l.

A third indicating lamp llt) is connected across wires 60 and 61 by acircuit from wire 60 consisting of Wire 89, indicating lamp 110,normally open contact lll of selector switch 99 to Wire 6l.

This circuit operates as follows.

When all ofthe push buttons are released, contactor CR Y is energized bythe circuit from wire 60 through wire 89, contacts S and Se, wire ht),Winding 91 of contactor CR, wire 92, contacts 87 and 88, and Wire 93 towire 6l. Contactor CR operates to close contacts CRl to CR@ and opencontacts CR7 to CRN. v

Should any of the normally open contacts of the push buttons be shorted,this fault is automatically indicated at this time and operation of thepress is prevented since an unsafe condition may possibly exist.

If the short exists across contacts S3, latch relay ILSR is energized bythe circuit from Wire 60 through contact CRZ, shorted contact 83,contact itil, contact CRL latch Winding 94 of latch relay lSR, wirel 92,contacts S7 and 88, and wire 93 to wire 6l.

If the short exists across contacts 84, latchl relay lSR is energized bythe circuit from wire 60 through shorted contact 84, contact 100,contact CRll, latch winding 94 of latch relay TSR, Wire 92, contacts S7and 38, and wire 93 to wire 61.

When latch winding 94 of latch relay lSR is energized, it operates toclose contact lSRll and open contacts lSRZ and lSR. The closing ofcontact lSRl connects indicating lamp llti across wires o@ and 61 toilluminate it, giving a visual indication that a short exists. Theopening of contacts lSRZ and lSRS opens the energizing circuitrforcontactor ZCR so it cannot be operated, thereby preventing theenergization of contactor SCR and Winding 37, and operation of thepress.

lf a short exists acrosscontacts 8l, latch relay ZSR is energized by thecircuit from wire 69 through wire S9,

contacts 85 and 86, wire 9d, latch Winding 162 of latch v relay ZSR,contact CRS, contact ltlS, and shorted contact 8l to wire 6l. Y Y

ita short exists across contact 82, latch relay ZSR is energized by thecircuit from wire et) through wire 89,

contacts S5 and 86, wire 99, latch winding to2 ot latchV relay 23R',contact CRS, contact N4, shorted Contact 32,

and contact CRA to wire 6l.

When latch winding 192 of latch relay ZSR is energized, it operates toclose contact 2SRl and open contacts ZSRZ and ZSRS. The closing ofcontact ZSRlY connects indicating lamp lltlv across wires o@ and el toilluminate it, giving a visual indication that a short exists. Theopening of contacts ZSRZ and ZSRS opens the energizing circuit Y forcontactor ZCR so it cannot be energized, thereby preventing theenergization of contactor SCR and winding 37, and operation of thepress. Y g

Latch relays lSR and ZSR are of the well known type where the contactsare operated by'energirzation ofthe Y latch winding, and once operated,the contacts are mainl2 tained operated by a mechanical latchindependent of the energization of the latch winding. Subsequentenergization of the trip winding after deenergization of the latchwinding releases the contacts so they can return to their unoperatedcondition.

Therefore, indicating lamp 107 remains illuminated and the energizingcircuit for contactor ZCR remains open even though the push buttons maylater be depressed.

After the shorted contact of the push button has been repaired, thecircuit energizing the latch winding becomes open. To reset the circuitso the press can be operated, contact 105, which may be a contact of apush button or other suitable device, is closed. This energizes tripwindings 95 and 103 of latch relays ISR and ZSR, respectively, to, asdescribed, release the latch mechanism and allow their contacts tobecome unoperated.

The press may now be operated as follows.

Contactor CR is operated as described when all the push buttons arereleased.

Winding 53 of contactor lCR is now energized by the circuit from Wirethrough contact CRS, winding 53, and contact CRS; to wire 6l. ContactorlCR operates to close contacts lCRl to 1CR4 and open contacts lCRS andlCR6. v

Push buttons 77, 78, 79 and 84B can now be depressed to open theircontacts 85, Y8o, 87 and 88. This de-energizes winding 91 of contactorCR, causing its contacts to become unoperated.

Contacter llCR remains operated by the circuit through contacts ZCRo andICR] connected in series with each other and in parallel with contactCRS, and contacts lCRZ and 2CR7 which are connected in series With eachother and in parallel with contact CR6.

The depression ot the push buttons also close contacts Y 8l, 82, S3 and84 to operate contactor 2CR. lts winding SCR is energized through thecircuits consisting of con`V tacts S4, CR7, 83, CRl, lSRZ, ZSRZ, 2CR3andrlCRS to winding 65, and thence through contacts 33, lCRo, 2CR4,ZSRS, ESR, CR9, 82, CRM and 8l. Winding 37 is energized through contactsSCRL SCRS, 3CR4 and SCR?. Yin addition to the above described circuitexcept for Winding and contact 33. The'details o'operation for thiscircuit are the same as described for FIGURE l, which for the `sake ofbrevity will not be repeated.

While I have described this feature connected in a circuit that utilizesfour `push buttons, it is understood that the feature is operable in acircuit having any number of push buttons. This is accomplished bymaking a separate circuit available for each normally open contact ofeach of the push buttons through which one of the latch windings oflatch relays lSR or ZSR can be energized.

Selector switches @7 and 99 have been included in the circuit to permitthe use of dummy plugs. Their use is well known in the art ofpresslcontrol and they are used to close both the normally open andclosed contacts of the push buttons. The purpose is to reduce the numberof push buttons required, when a fewer number of operators are needed tooperate the press. V v V Y To replace an operator in FlGURE 6, adurnrnyplugY may be inserted for push buttons 78 and 79. VThis closescontacts 82, 83, 86 and S7, vand if no changes are made in the circuit,latch relays lSR and ZSR would operate to indicate that contacts 82 and33 were shorted.Y Also, the operation of latch relays lSR and ZSR would,as described, prevent energization of vwinding 37 and operation ofthepress.

Y YThe operationY of latch relays llSR and ZYSR is prevented Y areas??by turning selector switch 97 to close contacts 96 and 109, and opencontacts 101 and 104. The opening et contact 101 prevents latch relaylSR from being energized through the new closed contact 83. The openingof contact 104 prevents latch relay 23R from being energized through thenew closed contact 82. The closing of contact 109 connects indicatinglamp 108 to wire 61 and by wire 89 to wire 60 se it is illuminated teindicate that one set of dummy plugs have been inserted for push buttons78 and 79.

It is seen that if all the push buttons are replaced by the dummy plugsthe press will not operate because of the operation of contacter CR, butit still would create an undesirable and potentially unsafe condition.Therefore, it is further protected against, since if both selectorswitches 97 and 99 are not turned to the dummy plug position, latchrelays 1SR and/or 2SR will operate. lf both selector switches are turnedto the dummy plug position, contacts 96 and 98 will be closed toenergize latch winding 94 of latch relay 1SR from wire 60 throughcontacts 96 and 98, winding 94, wire 92, contacts 07 and 88, and wire 93to wire 61. Latch relay 1SR thus operates te prevent operation of thecircuit and indicate by lamp 107 that something is Wrong, as has beenpreviously described.

It is to be noted that one selector switch is required for each pair ofpush buttons or for each operator.

FIGURE 6 also illustrates another safety feature which may beincorporated with the circuits of FIGURES l and if desired. This safetyfeature is to provide protection against the faulty operation of thelimit switch contacts or the disconnection of the limit switch from thepress. To achieve this safety feature, a fifth cam and a contact 112operated thereby must be added to the limit switch in FIGURE 2 and asecond limit switch having three cams and cam operated contacts 113,114, and 115 must be connected directly te shaft of the press (notshown).

These contacts are connected to operate in the circuit of FIGURE 6 asfollows.

Contact 115 of the second limit switch is connected in FIGURE 6 in thesame manner that contact 32 is connected in FIGURES l and 5. That is,between Contact 3CR2 and wire 61. Contact 32 is connected in series withcontact 114 between wire 61 and selector switch contact 55. Contact 113is connected in parallel With contact 32 and Contact 112 is connected inparallel with contact 114. The contacts of the cam operated limitswitches of FIGURE 6 operate in the sequence shown by the diagrammaticrepresentation of FIGURE 7.

Contacts 30, 31 and 33 of FGURE 6 operate in the same manner describedfor them in FIGURE l and contact 115 operates the same as described forcontact 32 in FIGURE 1. That is, contact opens at approximately the 180point to de-energize winding 62 of contacter ZCR and reclese atapproximately the 270 point to permit jumping the press as described.Contacts 31 and 115 close at approximately the 170 point to allow theoperators to release the push buttons without stopping ythe press andreopen at the end of the press cycle. Contact 33 opens at approximatelythe 200 point and then recloses at the 250 point te insure that contact2CR has operated properly, and if not to stop the press. The details ofoperation for these contacts in the circuit is set forth in thedescription for FlGURE l and for the sake of brevity will not berepeated here.

At the beginning of the press cycle, contacts 32 and 114 are closed andcontacts 112 and 113 are open. Therefore, the circuit from wire 61 towire 45 is completed through contacts 32 and 114 and Contact S5.

At approximately the 60 point in the press cycle, centacts 112 and 113close and at about the 70 point contacts 32 and 114 open. New thecircuit from wire 61 to wire is completed through contacts 112 and 113.

Contacts 32 and 114 reclese at about the 90 point and Cil 14 contacts112 and 113 re-epen at about the 100 point to transfer the circuit backthrough contacts 32 and 114.

If either of the limit switches had become broken or disconnected fromshaft 10 at a point in the press operating cycle when either contact 112er 113 was open, then when the above described transfer of the circuittook place to contacts 112 and 113, the press would stop immediatelybecause the open contact disconnects the source of power from thecircuit.

Had the limit switch breken or become disconnected with either of thecontacts 112 or 113 were closed, an unsafe condition would not occur. Itis seen that when centacts 112 and 113 are closed, contacts 31 and 115are open.

Therefore, when the press reached the point for closing contacts 31 and115 only one would do so and the other would remain open to prevent theenergizatien ef contacter `CR and winding 37 from being transferred fromthe normally closed contacts of the push buttons. Thus, as soon as theoperator released his hands from the push buttons, the press would stopregardless of its position. rThis gives the indication that Something iswrong which should be corrected and makes the condition safe bycompelling the operators hands to be on the push buttons.

Although I have described my invention with a certain degree efparticularity, it is understood that the above disclosure has been madeonly by way of example as required by law and that many changes in thedetails of circuitry may be resorted te by those skilled in the artwithout departing from the spirit and the scope of my invention ashereinafter claimed.

I claim:

1. A circuit for controlling energization of a work device comprising afirst, second, and third contacter; each contacter having a plurality ofnormally open closed contacts; a source of electrical power; an operatorpush button having a normally open and a normally closed contact; saidtirst contacter energized through the normally closed contact of thepush button and sustained energized through a normally closed contact ofthe second contacter and a normally open Contact of the rst contacter;upon depression of the operator push button, the second contacter isenergized through the normally open contacts of the push hutten and anormally open Contact of the first contacter means, and sustainedenergized by a normally open contact of the second contacter; and thethird contacter is energized through the normally open contacts of thepush button and a normally closed contact of the first contacter and anormally open Contact of the second contacter; and the device isenergized through the push button normally open contact, a normallyclosed contact 'of the first contacter, a normally open contact of thesecond and third centactors.

2. A circuit for controlling"energization of a Work device comprising afirst, second, and third contacter; each contacter having a plurality ofnormally open and normally closed contacts; a source of electricalpower; an operator push button having a normally open and a normallyclosed contacter; said first contacter energized from the source throughthe normally closed contact of the push button and sustained energizedthrough a normally closed contact of the second contacter and anerrnally open contact of the first contacter; upon depression of thepush hutten, the second contacter is energized from the source throughthe normally open contact of the push button and a normally open contactof the rst contacter' and sustained energized by a lirst and deviceoperated switch and a normally open contact of the second contacter; andthe third contacter is energized through the normally open contact ofthe push button, a normally closed contact of the iirst contacter and anormally open contact of the second contacter; and the device isenergized through the push button normally open contact, a normallyclosed contact of the first conmally open contact of the firstcontactor; upon depression of the push button, the second contactor isenergized from the source through the normally open contacts of the pushbutton and a normally open contact of the first contactor and sustainedenergized by a first device operated switch connected in parallel with anormally closed contact of the third contactor, and hoth connected inkseries with a normally open Ycontact of the second contactor; and thethird contactor is energized through the normally open contact of thepush button, a" normally closed contact of the first contactor and anormally open contact of the second contactor; and the device isenergized through the push button normally open contacts,

- vnormally closed contacts of the first contactor, and a normally opencontact of the second and third contactors. 4. A circuit for controllingenergization of a work ydevice comprising a first, second, and a thirdcontactor each contactor having a plurality of normally open andnormally closed contacts; a source of electrical power; an operator pushbutton having a normally open and a normally closed contact; said firstcontactor energized from the'source through the normally closed contactof the push button' and sustained energized through a normally closedcontact of lthe second contactor and a normally open contact of saidfirst contactor; upon depression of the push button, the secondcontactor is energizednfrorn the source through the push button normallyopen contact anda normally open contact of the Yfirst contactor andsustained energized through a norrnally open contact of the secondcontactor; and operation of the second contactor causes its normallyclosed contact in the sustaining circuit of the first contactor to(le-energize the first contactor; and the third contactor is energizedthrough the normally open Contact of the push button, a normally closedcontact of the first contactor, and a normally open contact of thesecond conmally open Contact of the push hutten, a normally closedcontact of the first contactor, and a normally open convtact of thesecond and third contactor.

5. A latchiru7 circ-uit comprising a iirst and second contactor; eachcontactor having a plurality of normally open and normally closedcontacts; a source of electrical power; an operator push button having anormally open and a normally closed contact connected inthe circuit;said first contactor energized through the normally closed contact ofthepush button and sustained energized through a normally closed contact ofthe second contactor and a normally open contact of the rst contactor;and upon depression or" the push button, saidl second contactor isenergized through the normally open contact of the push button and anormally open contact of the first contactor and sustained energized bya normally open contact Vof the second contactor, and said firstcontactor remains energized until'rsaid second contactor is operated toopen Vits'noriiially closed contact in the sustaining circuit of thefirst contactor.

6. A circuit for energizing a Worlr deviceto control a cyclicallyoperating machine comprising a first, second, and third contactor; eachcontactor having a plurality of normally open and normally closedcontacts; aV source Y of electrical power; an operator pushVbuttonhaving a normally open and a normally closed Contact; said firstcontactor energized from the sourcethrough `the normali Ytactor; and thework device is energized through the norclosed'contact of the pushbutton and sustained energized through a normally closed contact of thesecond contactor and a normally open contact of said first contactor;upon depression or the push button, the second contactor is energizedthrough the normally open contact of the push button and a normally opencontact of the first contactor and sustained energized through anormally open contact or the second contactor; and the third contactoris energized through the normally open Contact of the push button,normally closed contacts of the first contactor and a normallyopen'contact of the second contactor; and the device is energizedthrough the normally open contact of the push button, a normally closedcontact ol the first contactor and a normally open Contact of the secondand third contactors, and a first normally open machine operated switchVis set to close at a safe point in the machines cycle of operation toconnect the source to energize the third contactor and the work devicedirectly through a normally open contact of the third contactor.

7. A circuit for energizing a work device to operate a cyclicallyoperating machine as described in claim 6 wherein a normally closedsecond machine operated switch is connected in the sustaining circuit ofthe second contactor and Vset Vto open at a point in the machine cycleafter the closing of the firs-t machine operated switch to therebycle-energize said second contactor.

8. A circuit for energizing a work device for operating a cyclicallyoperating machineas set forth in claim 7 wherein a normally closed thirdmachine operated switch is connected in the energizing circuit of thethird con- Vtactor and has a normally closed contact'of the secondcontactor connected in parallel with said third machine operated switch,and whereby said third machine operated switch is arranged to be openedmomentarily after opening or said second machine operated switch toinsure that said second contactor means has become unoperated.

9. A circuit for energizing a work device to control a cyclicallyoperating machine comprising, a first, second,` and third contactor;each contactor having a plurality of normally open and normally closedcontacts, a source of electrical power; an operator push button having anormally open and a normally closed contact; said first contactorenergized from the source through the normally closed Contact of thepush button and sustained energized through a normally closed contact ofthe second contactor and a normally open Contact of said firstcontactor; upon depressionY of the push button,`the second contactor isenergized through the normally open Contact of the push ybutton and anormally open contact of the first contactor and sustained energizedthrough a normally closed first machine operated switch connected inparallel with a normally closed contact of the third contactor and bothin series with a normally Vopen contact of the second contactor; andafter the second contactor is energized, the first contactor iscle-energized by the opening of the Y normally closed contact in itssustaining circuit; and the VVthird contactor is energized through thenormally open contact of the push button, normally closed contacts ofthe first contactor and a normally open contact of the second contactor;and the device is energized through the normally openy contact of thepush button, a normally closed Contact ofY the rst contactor, a normallyopen Contact of the second and third contactor. l

l0. Al circuit for energizing a work device .for controlling acyclically operating machine comprising a first, second and thirdcontactor; each contactor having a plurality of normally open andnormally closed contacts; a

source of electrical power; an operator push button having Va normallyopen and a normally closed Contact; said first contactor energized fromthe source through the normally Y Y closed Contact of the push buttonYand sustained energized through a normally closed contact ofthe secondcontactor andenormally open contact of said tlrst contactor; upondepression of the push button, the second contactor'is energized throughthe normally open contact of the push button and normally open contactof the first contactor and sustained energized by a normally closedfirst machine operated switch and a normally open contact of the secondcontactor; whereby operating of the second contactor opens thesustaining circuit to the first contactor causing it to becomeunoperated; and the third contactor is energized through the normallyopen contact of the push button, normally closed contacts of the firstcontactor, normally closed contacts of the second contactor, and anormally closed second machine operated switch; a normally closedContact of the second contactor is connected in parallel with saidnormally closed second machine operated switch; whereby the device isenergized through the normally open contact of the push button, normallyclosed contacts of the rst contactor, normally open contacts of thesecond contactor and normally open contacts of the third contactor tostart operation of the cyclically operating machine and after its unsafeportion of operation, a normally open third machine operated switchcloses to connect the third contactor to the source through its ownnormally open contact and said parallel connected second machineoperated switch and normally closed contact of the second contactor, andalso connects the work device to the source through normally opencontacts of the third contactor thereby allowing release of said pushbuttons, and said first machine operated switch is set to open tode-energize the second contactor, and thereafter said second machineoperated switch opens momentarily to insure said second contactor hasbecome unoperated and at the end of said machines operating cycle, saidthird machine operated switch opens to de-energize the third contactorand the work device to stop the machine.

11. A circuit for controlling a cyclically operating machine as setforth in claim wherein a normally closed contact of the third contactoris connected in parallel with the normally closed first machine operatedswitch to prevent it opening from de-energizing the second contactoruntil after the third contactor has been energized.

12. A latching circuit comprising a first, second, and third contactor;each contactor having a plurality of normally open and normally closedcontacts; a source of electrical power; a pair of operating pushbuttons, each having a normally open and a normally closed contact; saidfirst contactor energized from the source through the normally closedcontact of one of said push buttons and having a sustaining circuit ofone of its normally open contacts and a normally closed contact of saidthird contactor; said second contactor energized from the source throughthe normally closed contacts of the other push button and having asustaining circuit containing one of its normally open contacts and anormally closed contact of said third contactor; and upon depression ofsaid push buttons said third contactor is energized through the pushbuttons normally opened contacts and a normally open Contact of saidfirst and second contactor, said third contactor having a sustainingcircuit through the normally open contacts of the push buttons and itsnormally open contacts, whereby said first and second contactors becomeunoperated due to the opening of said normally closed third con-tactorcontacts in their sustaining circuit.

13. A circuit for controlling energization of a work device comprising afirst, second, third, and fourth contactor; each contactor having aplurality of normally open and normally closed contacts; a source ofelectrical power; a pair of operator push buttons, each having anormally open and a normally closed contact; said first contactorenergized through a normally closed contact of one of said push buttonsand sustained energized through one of its normally open contacts and anormally closed contact of said third contactor; said second contactorenergized through the normally closed contact of the other push buttonand sustained energized through one of its normally open contacts and anormally closed contact of said third contactor; said third contactorenergized through the normally open contact of said push bu-ttons and anormally open contact of said first and second contactors and sustainedenergized through the normally open contacts of said push buttons andone of its normally open contacts; said fourth contactor energized fromthe source through the normally open contact of said push buttons and anormally closed contact of said first and second contactors and anormally open contact of said third contactor; and said work deviceenergized through said normally open contact of both push buttons, saidnormally closed contacts of said first and second contactors, normallyopen contacts of said third contactor, and normally open contacts ofsaid fourth contactor.

14. A circuit for energizing a work device to control a cyclicallyoperating machine comprising a first, second, third, and fourthcontactor; each contactor having a plurality of normally open landnormally closed contacts; a source of electrical power; a pair ofoperator push buttons, each having a normally open and a normally closedcontact; said first contactor energized through a normally closedcontact of one of said push buttons and sustained energized through oneof its normally open contacts and a normally closed contact of saidthird contactor; said second contactor energized through the normallyclosed contact of the other push button and sustained energized throughone of its normally open contacts and a normally closed contact of saidthird contactor; said third contactor energized through the normallyopen contact of said push buttons and a normally open contact of saidfirst and second contactors and sustained energized through the normallyopen contacts of said push buttons and one of its normally opencontacts; and after the third contactor is energized, the first andsecond contactors are de-energized by the opening of said normallyclosed third contactor contacts in their sustaining circuit; said fourthcontactor is energized from the source through the normally open contactof said push buttons and a normally closed contact of said first andsecond contactors and a normally open contact of said third contactor;and said work device energized through said normally open contact ofboth push buttons, said normally closed contacts of said first andsecond contactors, normally open contacts of said third contactor, andnormally open contacts of said fourth contactor to operate the machine,and a first normally open machine operated switch set to close ata safepoint in the machine cycle of operation to connect the source throughnormally open contacts of the fourth contactor and maintain the fourthcontactor and the work device energized and the machine operating.

15. A circuit for energizing a work device to operate a cyclicallyoperating machine as described in claim 14 wherein a normally closedsecond machine operated switch is connected in the sustaining circuit ofthe third contactor and set to open at a point in the machine cycleafter the closing of the first machine operated switch to therebyde-energize said third contactor.

16. A circuit for energizing a work device to operate a cyclicallyoperating machine as described in claim 15 whereln a normally closedcontact of the fourth contactor is connected in parallel with the secondmachine operated switch to thereby insure that the fourth contactor isenergized before the third contactor can be de-energized by opening ofthe second machine operated switch.

17. A circuit for energizing a work device to operate a cyclicallyoperating machine as described in claim 16 wherein a normally closedthird machine operated switch is connected in the energizing circuit ofthe fourth contactor and has a normally closed contact of the thirdcontactor connected in parallel with said third machine operated switch,and whereby said third machine operated switch is arranged to be openedmomentarily after opening of said second machine operated switch toinsure that said third contactor has become unoperated.

18. A circuit for detecting a shorted condition of normsgstr? mally opencontacts of an operable push button which are connected to energize anoperating circuit from a source of electrical power comprising; normallyclosed contacts on said push button; a first contactor having a normallyopen contact and an operating means connected to be energized from thesource through the normally closed push button contacts to close saidnormally open control of said first contactor; indicating meansconnected in series with the source, the normally closed push buttoncontacts, the normally open contact of the first contactor, and thenormally open push button contacts whereby if the said normally openpush button contacts are in a shorted condition when the push button isin its normal position said indicating means is energized.

19. A detecting circuit as set forth in claim 18 wherein the indicatingmeans is a second contactor having normally closed contacts connected inthe operating circuit whereby if said normally open push button contactis shorted said second contactor is energized to open itsv contacts andde-energize the operating circuit.

20. A detecting circuit as set forth in claim 18 wherein the indicatingmeans is a latch relay having normally closed contacts connected in theoperating circuit whereby if said normally open push button contact isshorted said latch relay is energized to open its contacts to make andmaintain the operating circuit until the latch relay is reset.

2l. A circuit for detecting a shorted condition of normally opencontacts connected in series to energize an operating circuit from asource of electrical power comprising; a plurality of push buttons, eachhaving a said normally open contact and a normally closed contact; afirst contactor having normally open and normally closed contacts, andconnected to be energized from the source through the normally closedpush button contacts; a second contactor connected to be energized fromthe source through the normally closed push button contacts and aplurality of isolated circuits, each circuit having a normally open pushbutton contact and at least one normally open contact of said firstcontactor and said circuits made isolated by the normally closedcontacts of the rst contactor, whereby if one of the normally open pushbutton contacts is shorted, the second contactor is energized.

22. A circuit for detecting a short circuit condition as described inclaim 2l wherein the second contactor has normally closed contactsconnected in the operating circuit whereby when said second contactor isenergized, it opens its contacts to cle-energize the operating circuit.

23. A circuit for controlling energization of a work device comprising afirst, second, third, and fourth contactor; each contactor having aplurality of normally open and normally closed contacts; a fifthcontactor having a normally closed Contact; a source of electrical powerfor energizing the contactors and work device; an oper* ators pushbutton having a normally open and a normally closed contact; the firstcontactor connected to be energized through the normally closed pushbutton contact; the fifth contactor connected to be energized throughthe normally closed push button contact and through a separate circuitcontaining the normally open push button contact and at least onenormally open contacts of said first contactor, said separate circuitestablished by a normally closed contacts of said first contactor; saidsecond contactor energized through a normally open contact of the firstcontactor and maintained energized through one of its normally opencontacts and a normally closed contact of said third contactor; saidthird contactor energized through the normally closed contact of thepush button, a normally closed contact of the first and fifth contactorand a normally open contact of the second contactor, and sustainedenergized through one of its normally open contacts; said fourthcontactor energized through a normally closed contact of first andsecond and fifth contactor, and a normally open contact of said thirdcontactor; said work device energized through a riormally closed contactof the first and second and fifth contactor, and a normally open contactof the third and fourth contactor.

24. A circuit for controlling energization of a workk device comprisinga first, second, third, and fourth contactor; each contactor having aplurality of normally open and normally closed contacts; a fifthcontactor having a normally closed contact; a source of electricalpowerV for energizing the contactors and work device; a plurality ofoperators push buttons, each having a normally open and a normallyclosed contact; the first contactor connected to be energized throughthe normally closed push buttonV contacts; the fifth contactor connectedto be energized through the normally closed push button contacts and aplurality of separate circuits; each separate circuit containing one ofthe normally open push button contacts and at least one normally opencontacts of said first contactor and established by normally closedcontacts of said first contactor; said second contactor through normallyopen contacts of the first contactor and maintained energized throughone of its normally open contacts and a normally closed contact of saidthird contactor; said third contactor energized through the normallyclosed contacts of the push buttons, Va normally closed contact of thefirst and fifth contactor and a normally open contact of the secondcontactor, and sustained energized through one of its normally opencontacts; said fourth contactor energized through a normally closedcontact of first and second and fifth contactor, and normally openconta-cts of said third contactor; said work device energized through anormally closed contact of the first and second and fifth contactor, anda normally open contact of the third and fourth contactor.

25. A circuit for energizing a work device to control a cyclicallyoperating machine comprising a first, second, third, and fourthcontactor; each contactor having a plurality of normally open andnormally closed contacts; a fifth contactor having a normally closedcontact; a source of electrical power for energizing said contactor andwork device; and operators push button having a normally open andnormally closed contact; said first contactor connected toY be energizedthrough the normally closed push button contact; said fifth contactorconnected to be energized through the normally closed push buttoncontact, a normally open push button contact and normally open contactof the first contactor; Said second contactor energized through anormally open contact of the first contactor and sustained energizedthrough one of its normally open contacts and a normally closed contactof the third contactor; and upon depression of said push button saidfirst contactor is deenergized and said third contactor is energizedthrough the normally open contact of the push button, a normally closedcontact of said rst and fifth contactor and a normally open contact ofsaid second contactor, and sustained energized through one of itsnormally open contacts; said second contactor becoming de-energized bythe opening of the normally closed Contact of the third contactor in itsenergizing circuit; said fourth contactor energized through the normallyopen contact of the push button, a normally closed contact of said firstand second and fifth contactors, and a normally open contact of saidthird contactor; said work device energized through the normally opencontact of the push button, a normally closed Contact of said first andsecond and fifth contactors, and a normally open contact of said thirdand fourth contactors to operate the machine, and a rst normally openmachine operated switch set to close at a safe point in the machinesoperating cycle whereby the fourth contactor and the work device aremaintained energized through said switch and a normally `open contact ofthe fourth contactor to keep the machine operating.

26. A circuit for energizing a work device to control a cyclicallyoperating machine comprising a first, second,

third, and fourth contactor; each contactor having a plurality ofnormally open and normally closed contacts; a fifth contactor having anormally closed contact; a source of electrical power for energizingsaid contactor and work device; a plurality of operators push buttons,each having a normally open and normally closed contact; said fir-stcontactor connected to be energized from the source through the normallyclosed push buttons contacts; said fifth contactor connected to beenergized through the normally closed push buttons contacts and aplurality of separate circuits, each separate circuit containing one ofthe normally open push button contacts and at least one normally opencontact of said first contactor and established by normally closedcontacts of said first contactor; Said second contactor energizedthrough normally open contacts of the first contactor and sustainedenergized through one of its normally open contacts and a normallyclosed contact of the third contactor; and upon depression of said pushbutton said first contactor is de-energized and said third contactor isenergized through the normally closed contacts of the push button, anormally closed contact of said first and fifth contactor and a normallyopen contact of Said second contactor, and sustained energized throughone of its normally open contacts; said second contactor becomingde-energized by the opening of the normally closed contact of the thirdcontactor in its energizing circuit; said fourth contactor energizedthrough the normally open contacts of the push buttons, a normallyclosed contacts of said first and second and fifth contactors and anormally open contact of said third contactor; said work deviceenergized through the normally open contacts of the push buttons, anormally closed contact of said first and second and fifth contactors,and a normally open contact of said third and fourth contactors tooperate the machine, and a first normally open machine operated switchset to close at a safe point in the machines operating cycle whereby thefourth contactor and the work device are maintained energized throughsaid switch and a normally open contact of the fourth contactor to keepthe machine operating.

27. A circuit for energizing a work device to control a cyclicallyoperating machine comprising a iirst, second, and third contactor; eachcontactor having a plurality of normally open and normally closedcontacts; a first and second limit switch operated by the machine, eachswitch having a plurality of contacts set to operate at variouspreselected points in the machines operating cycle; a source ofelectrical power for energizing the contactor and work device andconnected to the circuit through a normally closed first contact of eachlimit switch; a normally open second contact of each limit switchconnected in parallel with its respective normally closed contact; anoperator push button having a normally open and a normally closedcontact; said rst contactor energized through the normally closedcontact of the push button and sustained energized through one of itsnormally open contacts and a normally closed contact of the secondcontactor; upon depression of the push button, the second contactor isenergized through the normally open contact of the push button and anormally open contact of the first contactor and sustained energizedthrough one of its normally open contacts, and after the secondcontactor is energized, the first contactor is de-energized by theopening of the normally closed Contact in its sustaining circuit; thethird contactor is energized through the normally open contact of thepush button, a normally closed contact of the first contactor and anormally open contact of the second contactor; and the device isenergized through the normally open contact of the push button, anormally closed contact of the first contactor, a normally open contactof the second contactor and a normally open contact of the thirdcontactor to operate the machine and said second contacts of both limitswitches are set to close and immediately thereafter said first contactsof both limit switches open momentarily and then reclose, after whichsaid second contacts of both limit switches reopen to thereby check theoperation of both limit switches and if one should not be operating todisconnect the source of power from the circuit.

28. A circuit for energizing a work device to control a cyclicallyoperating machine comprising a iirst, second, and third contactor; eachcontactor having a plurality of normally open and normally closedcontacts; a first and second limit switch operated by the machine, eachswitch having a plurality of contacts set to operate at Variouspreselected points in the machines operating cycle; a source of electricpower for energizing the contactors and work device and connected to thecircuit through a normally closed first contact of each limit switch; anormally open second contact of each limit switch connected in parallelwith its respective normally closed contact; an operator push buttonhaving a normally open and a normally closed contact; said firstcontactor energized through the normally closed contact of the pushbutton and sustained energized through one of its normally open contactsand a normally closed contact of the second contactor; upon depressionof the push button, the second contactor is energized through thenormally open contact of the push button and a normally open contact ofthe first contactor and sustained energized through one of its normallyopen contacts and a normally closed Contact of the third contactor, andafter the second contactor is energized, the first contactor is(1e-energized by the opening of the normally closed contact in itssustaining circuit; a normally closed third contact of the first limitswitch connected in parallel with the normally closed contact of thethird contactor; and the third contactor is energized through thenormally open contact of the push button, a normally closed contact ofthe first contactor and a normally open contact of the second contactorand the second contactor remains energized through its normally opencontact and the third contact of the rst limit switch; and the device isenergized through the normally open contact of the push button, anormally closed contact of the first contactor, a normally open contactsof the second contactor and a normally open contact of the thirdcontactor to operate the machine, said second contacts of both limitswitches arranged to close and said first contacts of both limitswitches arranged to momentarily open and then reclose their contactsafter which said second contacts reopen in the unsafe portion of themachines cycle, and after said unsafe portion a normally open fourthcontact of the first limit switch and a normally open third contact ofthe second limit switch are arranged to close to maintain the thirdcontactor and Work device energized through said third and fourthcontacts and normally open contacts of the third contactor to keep themachine operating.

29. A circuit for energizing a work device to operate a cyclicallyoperating machine as described in claim 28 wherein a normally closedfifth contact of the first limit switch is connected in the energizingcircuit of the third contactor and having a normally closed contact ofthe second contactor connected in parallel therewith, and whereby saidfifth limit switch contact is arranged to be opened momentarily aftersaid third contact of the first limit switch opens to insure that saidsecond contactor has become unoperated, and if not, to de-energize thethird contactor and the work device to stop the machine.

30. A circuit for energizing a work device to control a cyclicallyoperating machine comprising a first, second, third, and fourthcontactor; each contactor having a plurality of normally open andnormally closed contacts; a first and second machine operated limitswitch,

areas?? each limit switch having contacts operated at variouspreselected positions in the machines cycle of operation; a source ofelectrical power for energizing the contactors and the werk device andconnected te the circuit through a normally closed first contact of eachlimit switch, a normally open second contact of the respective limitswitches connected in paral` l with the normally closed first contact; apair of operator push buttons, each having a normally open and anormally closed contact; said first contacter energized through anormally closed contact of one of said push buttons and sustainedenergized through one of its normally open contacts and a normallyclosed contact of said third contacter; said second contacter energizedthrough the normally closed contacts of the other push button andsustained energized through one of its normally open contacts and anormally closed contact of said third contacter; said third contacterenergized through the normally open contact of said push buttons and anormally open contact of said first and second contactors, and sustainedenergized through the normally open contacts of said push buttons andone of its nermally open contacts; and after the third contacter isenergized, the first and second contactors are de-energized by theopening of said normally closed third contacter contacts in theirsustaining circuits; said fourth contacter energized through thenormally open contacts of the push buttons, a normally closed contact ofsaid first and second contactors and a normally open contact of saidthird contacter; and said werk device energized through said normallyopen contact of the push buttons, a normally closed contact of saidfirst and second contactors and a normally open contact of said thirdcontacter and said fourth contacter to operate' the machine, and saidsecond contacts of both limit switches are set to close and immediatelythereafter said first contacts of beth limit switches open and thenreclese, and ysaid second contacts of both limit switches repoen tethereby disconnect the source from the c ircuit should either ef saidlimit switches not he operating properly.

3l. A circuit for energizing a work `device to control a cyclicallyoperating machine comprising la first, second, third, and fourthcontacter; each contacter having a plurality of normally open andnormally closed contacts; a first and second machine operated limitswitch, each limit switch having contacts operated at variouspreselected positions in the machines cycle of operation; a source ofelectrical power for energizing the contactors and the werk device, andconnected to the circuit through a normally closed first contact of eachlimit switch, la normally open second contact of the respective limitswitches connected in parallel with the normally closed first contact; apair of operator push buttons, each having a normally open and anormally closed Contact; said first centactor energized through anormally closed contact of one of said push buttons and sustainedenergized through one of its normally open contacts and a normallyclosed centact e-f said third contacter; said second contacter energizedthrough the normally closed contacts of the other push button andsustained energized through one of its normally open contacts and anorrnaly closed contact of said third contacter; said third f actorenergized and a normally open contact of said rst andV secondcontactors, and sustained energize-d through the normally open contactsof said push buttons and one of its normally open contacts and aparallel connected normally closed contact of the fourth contacter and athird contact of the first limit switch respectively; and after thethird contacter is energized, the first `and' second contactors arede-energized by the opening of said normally closed third contactercontacts in their sustaining circuits; said fourth contacter energizedthrough the non mally open contacts of the push buttons and a normallythrough the normally open contact or said push buttons Y closed contactof said first and second contactors; and a normally open contact of saidthird contacter; and said third contacter remains energized through itsnormally open Contact and the third contact of the first limit switch;and said werk device is energized through said normally open contact ofthe push buttons, a normally closed contact of said first and secondcontactors and a normally open contact of said third contacter and saidfourth centacter to operate the machine, said second contacts of bothlimit switches arranged to close and said first contacts of both limitswitches arranged to `open and then reclose after which said secondcontacts reopen in the unsafe portion ef the machines cycle, and aftersaid unsafe portion of the cycle a normally operi fourth contact of thefirst limit switch and a normally open third contact of the second limitswitch are arranged te close to maintain the fourth contacter and thework device energized through said third yand fourth contact andnormally open contacts of the fourth contacter to keep the machineoperating.

32. A circuit for energizing `a work device te operate a cyclicallyoperating machine as described in claim 3l wherein a normally closedfifth contact of the first limit switch is connected in the energizingcircuit ef the fourth contacter and having a normally closed contact ofthe third contacter connected in parallel therewith, and whereby saidfifth contact is arranged to he opened momentarily after said thirdContact of the first limit switch opens to insure that said thirdcontacter has become unoperated, and if not, to de-energize the thirdcontacter and the work device to stop the machine.

33, A circuit for energizing a work device te control a cyclicallyoperating machine comprising a first, second, third, and fourthcontacter; each contacter having a plurality of normally open andnormally closed contacts; a fifth contacter having normally closedcontacts; a first and second machine operated limit switch, each limitswitch having contacts set to operate at various preselected points inthe machines operating cycle; a source of electrical power forenergizing the contacter and the work device, `and connected te thecircuit through normally closed first contacts of hoth limit switches,each normally closed contact having a normally open contact of itsrespective limit switch connected in parallel therewith; an operatorpush button having a normally open and a normally closed contact; saidfirst contacter to be connected to energize through the normally closedcontact of the push button; said fifth contacter connected te beenergized through the normally closed contact of the push button, anormally open contact of the first contacter and riorinally open contactof the push button; said second contacter energized through a normallyopen contact of said first contacter and sustained energized through oneef its own normally open contacts and a normally closed contacts of saidthird contacter; and upon depression of said push button said firstcontacter is de-energized and said third contacter is energized throughthe norm-ally open contact of the push button, a normally closed centactof said first and fifth contactors, and a normally open contact of saidsecond contacter, and sustained en- Y ergized through one of itsnormally open contacts; and after the third contacter is energized, thesecond contacter is de-energized by the opening of said normally closedthird contacter Contact in its sustaining circuit; said fourth contacterisvene'rgized tlirougli'theV normally open contact of the push button, anormally. closed`con tact of the first and second and fifth contactors,and a normally open contact of the third contacter; and said werk deviceis energized through the normally open centact of said push button, anormally closed contact of said first and second and fifth contactors,and a normallf,l open contact of said third and fourth contactors teoper ate the machine whereby said second contacts of the limit switchesare operated` te close and immediately thereafter said first contacts ofthe limit switches are operated to open and reclose, and said secondcontacts are operated to reopen to thereby de-energize the circuit andstop the machine should either of the limit switches not be operatingproperly.

34. A circuit for energizing a work device to control a cyclicallyoperating machine comprising a first, second, third, and fourthcontactor; each contactor having 4a plurality of normally open andnormally closed contacts; a fifth contactor having normally closedcontacts; a rst and second machine operated limit switch, each limitswitch having contacts set to operate at various preselected points inthe machines operating cycle; a source of electrical power forenergizing the contactors and the work device, and connected to thecircuit through normally closed first contacts of both limit switches,each normally closed contact having la normally open contact of itsrespective limit switch connected in parallel therewith; a plurality ofoperators push buttons, each having a normally open and a normallyclosed contact; said first contactor connected to be energized throughthe normally closed contact o' the push buttons; said fifth contactorconnected to be energized through the normally closed contact of thepush buttons and a plurality of separate circuits, each separate circuitcontaining one of the normally open push button contacts and at leastone normally open contact of said rst contactor and established bynormally closed contacts of said first contactor; said second contactorenergized through a normally open contact of said first contactor andsustained energized through one of its own normally open contacts and anormally closed contact of said third contactor; and upon depression ofsaid push buttons said first contactor is deenergized and said thirdcontactor is energized through the normally open contact of said pushbuttons, a norm-ally closed contact of said first and fifth contactors,and a normally open contact of said second contactor, and sustainedenergized through one of its normally open contacts; and after the thirdcontactor is energized, the second contactor is de-energized by theopening of said normally closed third contactor contact in itssustaining circuit; said fourth contactor is energized through thenormally open contact of the push buttons, normally closed contact ofthe first and second and fth contactors, and a normally open contact ofthe third contactor; and said work device is energized through thenormally open contact of said push buttons, a normally closed Contact ofsaid first and second and fifth contactors, and a normally open contactof said third and fourth contactors to operate the machine whereby saidsecond contacts of the limit switches are operated to close andimmediately thereafter said first contacts of the limit switches areoperated to open and reclose, and said second contacts are operated toreopen to thereby deenergize the circuit and stop the machine shouldeither of the limit switches not be operating properly.

References Cited by the Examiner UNITED STATES PATENTS 2,250,141 7/41Thurston 307--113 X 2,676,293 4/54 Mudd 307-113 X 2,944,120 7/60 Ruben307-113 X LLOYD MCCOLLUM, Primary Examiner. MlLTON O. HIRSHFIELD,Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,183,377 May ll, 1965 Frank H. Holland It is hereby certified thaterror appears in the above numbered patent reqiring correction and thatthe said Letters Patent should read as eorreotedbelow.

Column Z, line ll, for "colsed" read Closed Column 14, line 35, after"open" insert and normally Column 19, line 8, for "Control" read ContactSigned and sealed this 23rd day of November 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER AIM-,sting Officer Commissioner ofPatents

33. A CIRCUIT FOR ENERGIZING A WORK DEVICE TO CONTROL A CYCLICALLYOPEATING MACHINE COMPRISING A FIRST, SECOND, THRID, AND FOURTHCONTACTOR; EACH CONTACTOR HAVING A PLURALITY OF NORMALLY OPEN ANDNORMALLY CLOSED CONTACTS; A FIFTH CONTACTOR HAVING NORMALLY CLOSEDCONTACTS; A FIRST AND SECOND MACHINE OPERATED LIMIT SWITCH, EACH LIMITSWITCH HAVING CONTACTS SET TO OPERATE AT VARIOUS PRESELECTED POINTS INTHE MACHINES OPERATING CYCLE; A SOURCE OF ELECTRICAL POWER FORENERGIZING THE CONTACTOR AND THE WORK DEVICE, AND CONNECTED TO THECIRCUIT THROUGH NORMALLY CLOSED FIRST CONNECTED OF BOTH LIMIT SWITCHES,EACH NORMALLY COLSED CONTACT HAVING A NORMALLY OPEN CONTCT OF ITSRESPECTIVE LIMIT SWITCH CONNECTED IN PARALLEL THEREWITH; AN OPERATORPUSH BUTTON HAVING A NORMALLY OPEN AND A NORMALLY CLOSED CONTACT; SAIDFIRST CONTACTOR TO BE CONNECTED TO ENERGIZE THROUGH THE NORMALLY CLOSEDCONTACT OF THE PUSH BUTTON; SAID FIFTY CONTACTOR CONNECTED TO BEENERGIZED THROUGH THE NORMALLY CLOSED CONTACT OF THE PUSH BUTTON, ANORMALLY OPEN CONTACT OF THE FIRST CONTACTOR AND NORMALLY OPEN CONTACTOF THE PUSH BUTTON; SAID SECOND CONTACTOR ENERGIZED THROUGH A NORMALLYOPEN CONTACT OF SAID FIRST CONTACTOR AND SUSTAINED ENERGIZED THROUGH ONEOF ITS OWN NORMALLY OPEN CONTACTS AND A NORMALLY CLOSED CONTACTS OF SAIDTHRID CONTACTOR; AND UPON DEPRESSION OF SAID PUSH BUTTON SAID FIRSTCONTACTOR IS DE-ENERGIZED AND SAID THIRD CONTACTOR IS ENERGIZED THROUGHTTHE NORMALLY OPEN CONTACT OF THE PUSH BUTTON, A NORMALLY CLOSED CONTACTOF SAID FIRST AND FIFTH CONTACTORS, AND A NORMALLY OPEN CONTACT OF SAIDSECOND CONTACTOR, AND SUSTAINED ENERGIZED THROUGH ONE OF ITS NORMALLYOPEN CONTACTS; AND AFTER THE THIRD CONTACTOR IS ENERGIZED, THE SECONDCONTACTOR IS DE-ENERGIZED BY THE OPENING OF SAID NORMALLY CLOSED THRIDCONTACTOR CONTACT IN ITS SUSTAINING CIRCUIT; SAID FOURTH CONTACTOR ISENERGIZED THROUGH THE NORMALLY OPEN CONTACT OF THE PUSH BUTTON, ANORMALLY CLOSED CONTACT OF THE FIRST AND SECOND AND FIFTH CONTACTORS,AND A NORMALLY OPEN CONTACT OF THE THRID CONTACTOR; AND SAID WORK DEVICEIS ENERGIZED THROUGH THE NORMALLY OPEN CONTACT OF SAID PUSH BUTTON, ANORMALLY CLOSED CONTACT OF SAID FIRST AND SECOND AND FIFTH CONTACTORS,AND A NORMALLY OPEN CONTACT OF SAID THRID AND FOUTH CONTACTORS TOOPERATE THE MACHINE WHEREBY SAID SECOND CONTACTS OF THE LIMIT SWITCHESARE OPERATED TO CLOSE AND IMMEDIATELY THEREAFTER SAID FIRST CONTACTS OFTHE LIMIT SWITCHES ARE OPERATED TO OPEN AND RECLOSE, AND SAID SECONDCONTACTS ARE OPERATED TO REOPEN TO THEREBY DE-ENERGIZE THE CIRCUIT ANDSTOP THE MACHINE SHOULD EITHER OF THE LIMIT SWITCHES NOT BE OPERATINGPROPERLY.